Purity >98% by NMR, TLC. LH-846 is a potent and selective inhibitor of casein kinase (CK) 1d., IC50s=0.29, 1.3 and 2.5 uM for d, e and a isoforms respectively with no inhibition of CK2. Inhibits CK1d-mediated phosphorylation and degradation of PER1 protein and lengthens circadian period in U2OS cells.